Maternal Age-Related Risks for Down Syndrome

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Maternal Risk after 35. Hero Images / Getty Images

The most common risk factor for Down syndrome is maternal age. In other words, as a woman gets older, her risk of having a pregnancy with a chromosome abnormality increases.

Maternal age risks are often presented in chart format as per below. In order to really understand the risk figures presented in this chart, it is important to understand how the data was collected and what it is actually telling you.

Overview of Maternal Age-Related Risk Chart

You may have seen different versions of maternal age-related risk charts noticed that there are differences in the risk numbers presented. There are a couple of reasons for these variations.

Some charts represent the maternal age-related risk for all chromosome abnormalities rather than just for Down syndrome. The chart below represents the age-related risk of having a child with Down syndrome (trisomy 21) only. 

Trisomy 21 is the most common chromosomal abnormality and occurs when a baby gets an extra chromosome 21 from his mother or father. There are other trisomies, like trisomy 18 or trisomy 13, but these are not as common as trisomy 21. Even so, Down syndrome is not that common, as only 1 in 700 babies is born with it. 

In summary, this chart illustrates the likelihood of having a child with Down syndrome, based on a mother’s age at the time of pregnancy.

For example, if you are 45 years old at the time of pregnancy, the chance of having a child diagnosed with Down syndrome at birth is 1 in 34 which is a little less than 3 percent.

Maternal Age-Related Risks

Mom's Age                   Risk for trisomy 21 (Down syndrome)                   
201 in 1,475 
   
251 in 1,340 
   
301 in 935 
   
351 in 350 
   
401 in 85 
   
45

1 in 34

 
   

Who Should Not Use This Chart

If you have had a previous child or pregnancy with trisomy 21, your risk may be different than the age-related risks presented in this chart. 

Also, if you have a family history of a chromosome translocation or a previous child with translocation Down syndrome, you should consult with a genetic counselor who can give you more specific information about your risk, depending on the type of translocation and your chromosome results. 

A translocation is a rare cause of Down syndrome and occurs when a parent has two copies of chromosome 21 plus an extra part of chromosome 21 or an entire chromosome 21 stuck to one of the normal copies of chromosome 21.

Finally, if you have conceived using a donor egg, you should use the age of the woman that donated the egg.

In all of these situations, it's best to talk to a genetic counselor to get an accurate assessment of your risks.

Moving Forward With Prenatal Testing

Women decide to undergo prenatal testing for Down syndrome for different reasons. Some want to know the health of their baby before he or she is born to better prepare for their newborn care, whereas other women feel like testing may ease their worries and allow them to better enjoy the pregnancy if the test is negative.

 

Whatever your reasons, if you choose to undergo prenatal testing for Down syndrome, be sure you fully understand the differences among the tests available.

For example, a screening test for Down syndrome may involve a blood test or an ultrasound or both. On the other hand, a diagnostic test for Down syndrome means undergoing chorionic villus sampling or an amniocentesis, which is invasive and does carry a small risk of miscarriage.

Interpreting a screening test for Down syndrome is also quite different from a diagnostic test. Remember, a screening test cannot tell you for certain if your baby has Down syndrome, while a diagnostic test can.

Neither test can predict the severity of problems your baby will have if Down syndrome is present. In the end, sorting out these details with your doctor is important so you feel confident and well-informed about your decision. 

A Word From Verywell

It's normal to worry about having a healthy baby. Talking with your doctor and/or a genetic counselor is helpful so you are knowledgeable about your risks, based on your unique situation.

If you have a baby with Down syndrome, know that with proper care and support, many children with this condition lead happy, fulfilling lives. In fact, the average life expectancy of a child born with Down syndrome is now between 50 and 60 years—truly remarkable. 

Sources:

Alldred SK et al. First trimester serum tests for Down's syndrome screening. Cochrane Database Sys Rev. 2015 Nov 30;(11):CD011975.

March of Dimes. (2016). Down Syndrome. 

Messerlian GM, Palomaki GE. Down syndrome: Overview of prenatal screening. In: UpToDate, Wilkins-Haug L (Ed), UpToDate, Waltham, MA.

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